Audi's engineers did a fairly poor job of concealing the Audi RS5, the much-anticipated super-super GT from Audi, from the KGP photographers patrolling the California desert. The revised and menacing front bumper, silver side mirrors and lack of fog lamps is a fairly sure giveaway that this is the supremely sporty version of the A5. The question is, what can't we see? Is it the reported 4.2-Liter V8 out of the Audi RS4 beneath that sexy hood or is the twin-turbo V10 out of the wicked Audi RS6 motivating this mule? Conjecture and spy report below the jump.

Spy Report It appears that we caught Audi engineers working on an RS5 prototype in the California desert. The aggressively revised front fascia carries all of the menacing design traits of Audi's other RS models, but it looks particularly fetching on the already seductive A5 coupe. The fog lamps have been removed in favor of extra breathing ducts to cool the engine and brakes—just as on Audi's recently-released RS6. This prototype doesn't yet have all the expected RS cues—namely the signature dual oval exhaust tips (it still has the quad oval tips from the S5)—but it is wearing silver side mirrors (another of Audi's RS design signatures). The RS6 sports some subtly flared bodywork, but it remains to be seen whether the RS5 will get a similar treatment. The other questions obviously focus around what's under the hood. The Audi RS6 is powered by the latest direct-injection, twin-turbocharged 5.2-liter V10, generating 580 hp at 6,250 rpm with 479 pound-feet of torque at just 1,500 rpm. A similar application in the RS5 would obviously be most welcome.